Cellulosic sponge process



United St tes Patent 2,853,395 CELLULOSIC SPONGE PROCESS Robert Otto Osborn, Snyder, N. Y., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application March 12, 1954 Serial No. 415,971

2 Claims. (Cl. 106122) This invention relates to the production of artificial sponge. More particularly, it relates to the production of cellulosic sponge from cellulosic solutions or dispersions such as viscose.

In the usual manufacture of artificial cellulosic sponge,

a pasty mass is prepared by mixing together viscose (cellulose xanthate dissolved in caustic soda solution), strength-giving fibers such as hemp or jute, and a soluble pore-forming substance such as sodium sulfate decahydrate. This mixture is placed in molds and coagulated and regenerated by means of heat and/ or the chemical action of a suitable solution. After coagulation and regeneration have been completed, the pore-forming substance is melted or washed from the mass; and the resulting cellulosic sponge-like material is Washed, dried and/or subjected to other finishing treatments, and then out into appropriate blocks. A well formed sponge produced in accordance with the process just described will have fibers uniformly distributed throughout the sponge structure. However, even though the fibers are incorporated in the viscose with thorough mixing, the fibers have a marked tendency to aggregate in clumps or knots which result in undesirable stiff lumps in an otherwise soft sponge.

An object of this invention, therefore, is to provide a process for producing substantially knot-free cellulosic sponges. Another object is to provide steps for the uniform and stable distribution of reinforcing (strengthgiving) fibers in a cellulosic sponge derived from viscose.

The foregoing and other objects will more clearly appear hereinafter.

These objects are realized by the present invention which, briefly stated, comprises dispersing reinforcing fibers in a liquid medium selected from the group consisting of water and dilute aqueous caustic soda solution, and thereafter mixing the resulting dispersion with cellulose xanthate whereby to form viscose having reinforcing fibers uniformly distributed therethrough. The fiber-containing viscose so produced is thereafter treated by known methods to form a cellulosic sponge structure; e. g., a soluble pore-forming substance is incorporated in the fiber-containing viscose to form a sponge mix which is placed in molds and is then coagulated and regenerated, after which the pore-forming substance is removed and the resulting cellulosic sponge structure is washed and dried.

Reference is made to United States Patent No. 2,295,- 823 for a full disclosure of the materials as well as the amounts and conditions that may be used in connection with the steps of the process of this invention for producing cellulosic sponges from viscose. It is to be understood, of course, that any fiber that will impart strength to the sponge structure, and that any suitable pore-forming substance, may be employed herein in place of the specific fibers and soluble pore-forming substances disclosed in United States Patent No. 2,295,823. Moreover, coagulation and/ or regeneration of the sponge mixture may be effected by any known expedient, and the Patented Spt. 23, 1958 "Ice.

resulting sponge structure may be subjected to any desired finishing treatments.-

The following example of a preferred embodiment further illustrates the principles and practice of this invention. Parts and percentages are by weight unless otherwise indicated.

EXAMPLE Ingredients are added to a mixer in the following order and mixed as specified:

The completed sponge mix is then placed in molds and is coagulated and regenerated by means of heat, as described in United States Patent No. 1,909,629 (Pfannenstiel et al.) or No. 2,133,810 (Craigue). The coagulated sponges are removed from the molds, washed, bleached, purified, dried and/ or subjected to other finishing treatments, and then cut into suitable blocks.

Examination of the sponge blocks reveals that knots are practically eliminated by the method of this invention. Knot values for sponges made according to the old method (adding fibers to the viscose) are given for comparative purposes. See Table I.

Table I KNOTS IN SPONGES Total Number of Knots 1% x 3% x 53 16 Oval-shaped sponge cut in half:

x 4 x 2 x45 "x7" 2 large blocks cut into strips wide 6 large blocks cut into strips 15 or 2.5 per Mg" wide.

block.

By reason of the improvement of the present invention, the reinforcing fibers are thoroughly wetted and dispersed before the mix becomes thick and viscous due to the addition of the cellulose xanthate. Another advantage of the present invention is that fibers difiicult to fiuif and, hence, heretofore rejected as reinforcing fibers in sponge structures, can now be used.

I claim:

1. In the manufacture of cellulosic sponges wherein viscose, reinforcing fibers, and a pore-forming substance are combined to form a sponge mix which is then coagulated, regenerated, and purified to form a sponge structure, the improvement which comprises the steps of dispersing said reinforcing fibers in a liquid medium consisting of a member selected from the group consisting of water and dilute aqueous caustic soda solution, and thereafter mixing the resulting dispersion with cellulose 3' i 4 xanthate, whereby to form viscose having reinforcing 2,266,313 Ehlers et a1 Dec. 16, 1941 fibers uniformly distributed therethrough. 2,331,936 Schiosser et a1. Oct. 19, 1943 2. The process according to claim 1 wherein said liquid 2,354,260 Haney et a1 July 25, 1944 medium is dilute aqueous caustic soda solution. 2,495,237 Petiton Jan. 24, 1950 5 References Cited in the file of this patent FOREIGN PATENTS UNITED STATES PATENTS 1 438,851 Great Britain Nov. 25, 1935 1,974,393 Mostny Sept. 18,1934 866,132 France June 18, 1941 

1. IN THE MANUFACTURE OF CELLUISOIC SPONGES WHEREIN VISCOSE, REINFORCING FIBERS, AND A PORE-FORMING SUBSTANCE ARE COMBINED TO FORM A SPONGE MIX WHICH IS THEN COAGULATED, REGENERATED, AND PURIFICED TO FORM A SPONE STRUCTURE, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF DISPERSING SAID REINFORCING FIBERS IN A LIQUID MEDIUM CONSISTING OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF WATER AND DILUTE AQUEOUS CAUSTIC SODA SOLUTION, AND THEREAFTER MIXING THE RESULTING DISPERSION WITH CELLULOSE XANTHATE, WHEREBY TO FORM VISCOSE HAVING REINFORCING FBERS UNIFORMLY DISTRIBUTED THERETHROUGH. 